Tailoring indium oxide nanocrystal synthesis conditions for air-stable high-performance solution-processed thin-film transistors

Semiconducting metal oxides (ZnO, SnO₂, In₂O₃, and combinations thereof) are a uniquely interesting family of materials because of their high carrier mobilities in the amorphous and generally disordered states, and solution-processed routes to these materials are of particular interest to the printed electronics community. Colloidal nanocrystal routes to these materials are particularly interesting, because nanocrystals may be formulated with tunable surface properties into stable inks, and printed to form devices in an additive manner. We report our investigation of an In₂O₃ nanocrystal synthesis for high-performance solution-deposited semiconductor layers for thin-film transistors (TFTs). We studied the effects of various synthesis parameters on the nanocrystals themselves, and how those changes ultimately impacted the performance of TFTs. Using a sintered film of solution-deposited In₂O₃ nanocrystals as the TFT channel material, we fabricated devices that exhibit field effect mobility of 10 cm²/(V s) and an on/off current ratio greater than 1 × 10⁶. These results outperform previous air-stable nanocrystal TFTs, and demonstrate the suitability of colloidal nanocrystal inks for high-performance printed electronics.